JPS60167275A - Temperature controller of fuel cell plant reformer - Google Patents

Abstract

PURPOSE:To prevent local increase in temperature in a reformer and keep catalyst temperature optimum by arranging a temperature detector in a tube near a heat source and increasing the amount of air according to the temperature difference when the detected temperature exceeded the setting temperature. CONSTITUTION:A catalyst temperature detector 11 is arranged at the end of tube 1A within a reformer 1, and a pilot burner fuel control valve 9 and a pilot burner air control valve 10 are controlled so that catalyst temperature C becomes setting temperature TRs1. A tube temperature 21 is set near a heat source of the tube 1A, and a main burner air control valve 8 is controlled so that tube temperature does not exceed a setting temperature. Thereby, local increase in temperature in the reformer is prevented and catalyst temperature within the tube is kept optimum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a temperature control device for a reformer in a fuel cell plant.

[Technical background of the invention and its problems] In a fuel cell plant, a reformer is used to reform a fuel such as natural gas into a fuel with a high hydrogen content. This reformer usually includes a double tube structure filled with a catalyst, and reforms the fuel by passing the fuel through the tube and causing a reforming reaction. The reforming reaction at this time is an endothermic reaction, so in order to obtain stable reformed fuel, it is necessary to heat the tube from the outside with a burner and maintain the catalyst temperature at an operating temperature suitable for reforming.

However, if an attempt is made to maintain the catalyst temperature up to the end of the tube at an optimum temperature in order to increase the reforming efficiency, a problem arises in that the temperature of the tube near the heat source rises too much and the tube and catalyst are destroyed. On the other hand, if we reduce the burner thermal power or increase the amount of fuel that passes through the reformer in order to prevent the tube temperature from rising too high, there will be parts where the catalyst temperature drops below the operating temperature, which is harmful to the fuel cell plant.
A problem arises in that the O acid component increases and the reforming efficiency decreases.

[Object of the Invention] An object of the present invention is to provide a temperature control device for a reformer that can maintain the catalyst temperature at an optimum operating temperature while suppressing local temperature increases in the reformer.

[Summary of the invention] For this reason, the present invention provides a temperature detector in the tube portion near the heat source, and when the detected temperature exceeds the set temperature, the amount of air supplied to the burner is increased according to the temperature difference. By doing so, it is possible to prevent a local temperature rise and maintain the catalyst temperature of the entire tube at an optimum temperature.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show a configuration diagram of a fuel cell plant reformer temperature control device according to an embodiment of the present invention.
For convenience of explanation, the drawing is shown divided into two parts, but they are actually integrated. Therefore, the fuel cell plant portion is shown overlappingly in two figures.

In these figures, 1 is a reformer and 2 is a fuel cell. The reformer 1 includes a double tube structure tube IA filled with a catalyst, and a main burner IB placed at the top of the tube.
and an air supply port IC that supplies the air necessary for its combustion.
1. The combustion engine is equipped with a pilot burner ID for heating the tube IA and an air supply port IE for supplying air necessary for combustion.

The fuel a supplied through the reforming fuel control valve 3 passes through the tube IA of the reformer 1 and is reformed into fuel with a high hydrogen content. This reformed fuel is transferred to the high temperature shift converter 4.
After passing through the low temperature transformer 5 and removing unnecessary components such as CO,
The reformed fuel is supplied to the hydrogen electrode 2A of the fuel cell 2 via the reformed fuel control valve 6.

On the other hand, air is supplied to the oxygen electrode 2B of the fuel cell 2 from a turbo compressor (not shown). Thereby, the fuel cell 2 generates electrical energy through a catalytic reaction between hydrogen in the hydrogen electrode 2A and oxygen in the oxygen electrode 2B such that the oxygen electrode 2B becomes a positive electrode and the hydrogen electrode 2A becomes a negative electrode. The generated DC output is converted into AC by the converter 7, and sent to the power grid as AC power.

A part of the hydrogen thus supplied to the hydrogen electrode 2A of the fuel cell 2 is consumed as electrical energy, and the rest is supplied to the main burner IB of the reformer 1 and burned. It takes about one hour from starting the fuel cell plant to heating the tube IA by the main burner IB, and during this time the tube IA must be heated by other means. Tube IA at startup of this fuel cell plant
Heating is performed by the pilot burner ID, to which fuel a is supplied via a pilot burner fuel control valve 9 and air is supplied via a pilot burner air control valve 10.

However, the tube IA due to this pilot burner ID
is heated only at startup, and once surplus hydrogen is sufficiently supplied from hydrogen electrode 2^ of fuel cell 2 to main burner IB of reformer L, pilot burner ID will be heated to the lowest flow rate that will not extinguish the flame. Fuel supply is limited.

In such a fuel cell plant, in order to maintain the catalyst temperature in the tube IA at the optimum operating temperature, a catalyst temperature detector 11 is installed at the end of the tube IA in the reformer 1, as shown in FIG. and the catalyst temperature C is the set temperature TRs
The flow rates of the pilot burner fuel control valve 9 and the pilot burner air control valve 10 are controlled so that the flow rate becomes 1.

That is, 12 is a comparator, 13 is a pilot burner fuel flow rate calculation control section, 14 is a fuel flow rate detector, 15 is a comparator, 1
Reference numeral 6 denotes an output control calculation section, 17 a function generator, 18 an air flow rate detector, 19 a comparator, and 20 an output control calculation section. The comparator 12 calculates the difference between the set temperature TRs and the detected temperature C, and the pilot burner fuel flow rate calculation control section 13 converts the difference into a pilot burner fuel flow rate command. The difference between this flow rate command and the actual flow rate from the fuel flow rate detector 14 is calculated by the comparator 15, and the difference between the flow rate command and the actual flow rate from the fuel flow rate detector 14 is
After the ID is calculated, the fuel flow rate to the pilot burner ID is controlled by being added to the pilot burner fuel control valve 9. At the same time, the pilot burner fuel flow rate command is also applied to the function generator 17, where an air flow rate command value corresponding to the fuel flow rate is calculated. The difference between the calculated flow rate command and the actual flow rate from the air flow rate detector 18 is calculated by the comparator 19, and the difference between the calculated flow rate command and the actual flow rate from the air flow rate detector 18 is calculated by the comparator 19.
After the calculation, the air flow rate is controlled by applying it to the pilot burner air control valve lO.

In this way, by controlling the fuel flow rate and air flow rate supplied to the pilot burner according to the catalyst temperature,
The catalyst temperature within the tube IA can be maintained at an optimum operating temperature for reforming the fuel.

Next, pilot burner ID or main burner IB
In order to prevent a local temperature rise in tube IA due to
As shown in FIG. 2, a tube temperature detector 21 is provided in a portion of the tube IA near the heat source to prevent the tube temperature from exceeding the set temperature TRs2.

The flow rate of the main burner air control valve 8 is controlled.

That is, 22 is a comparator, 23 is an air flow rate calculation section, 24 is an adder, 25 is an output current detector, 26 is a function generator, and 27
is a selector, 28 is an air flow rate detector, 29 is a comparator, 30
is an output control calculation section. When starting up the fuel cell plant, the selector 27 is switched to the air setting flow rate FRs side.
A comparator 29 calculates the difference between the set flow rate FRs and the actual flow rate from the air flow rate detector 28 . Normally, the difference is added from the adder 24 to the main burner air control valve 8 via the output control calculation unit 3o, so that air not related to combustion in the pilot burner ID is blown from the air supply port LC. Become. Thereby, the heat in the upper part of the tube is diffused, and local heating of the tube IA by the pilot burner ID at the time of startup is prevented. When heating the tube IA in this state, the difference between the detected temperature from the tube temperature detector 21 and the set temperature TRs2 is calculated by the comparator 22 and added to the air flow rate calculation section 23. This air flow rate calculation section 23 has a limiter that outputs only when the input is positive. Therefore, when the tube temperature exceeds the set temperature TRs 2, the difference is added to the adder 24 and acts to increase the air flow rate from the main burner air control valve 8 via the output control calculation section 30. As a result, the upper part of the tube IA is cooled, the tube temperature from the tube temperature detector 21 is pulled back to the set temperature, and local temperature rise is suppressed.

On the other hand, after the main burner IB is ignited, the current signal from the output current detector 25 of the fuel cell 2 is applied to the function generator 26, where it is converted into an air flow rate command commensurate with the fuel flow rate supplied to the main burner IB. . This air flow rate command is applied to the comparator 29 via the selector 27 which is being switched at that time, and the difference between it and the actual air flow rate from the air flow rate detector 28 is calculated. By applying this to the main burner air control valve 8 via the adder 24 and the output control calculation unit 30, the air supply port IC supplies just the amount of air necessary for burning the fuel in the main burner IB at that time. be done. In this state, as in the case of the pilot burner ID, if the detected temperature from the tube temperature detector 21 rises above the set temperature TRs2, the difference is added to the adder 24, and the air flow rate of the main burner air control valve 8 is increased. Increase. This prevents local heating of the tube IA.

In this way, by combining the catalyst temperature control circuit based on the fuel flow rate shown in FIG. 1 and the local temperature rise prevention circuit based on the air flow rate shown in FIG. 2, a local temperature rise in the tube IA of the reformer 1 can be prevented. Is that possible? *-? - You can keep the lamp at a long operating temperature.

[Effects of the Invention] As described above, according to the present invention, by adjusting the air flow rate to the reformer heating burner, it is possible to effectively prevent the temperature rise in the portion of the tube near the heat source without lowering the catalyst temperature. By uniformly heating the entire tube, the catalyst temperature can be maintained at the optimum operating temperature, and efficient reforming operation can be performed.

[Brief explanation of drawings]

1 and 2 are block diagrams of a fuel cell plant reformer temperature control device according to an embodiment of the present invention, and FIG. 1 is a block diagram of a catalyst temperature control circuit based on fuel flow rate, and FIG.
The figure is a configuration diagram of a circuit for preventing local temperature rise due to air flow rate. 1... Reformer, IA... Tube, IB... Main burner, IC, IB... Air supply port, ID...
Pilot burner, 2...Fuel cell, 2A...Hydrogen electrode, 2B...Oxygen electrode, 3...Reforming fuel control valve, 4
...High temperature shift converter, 5...Low temperature shift converter, 6...Reformed fuel control valve, 7...Converter, 8...Main burner air control valve, 9...Pilot burner fuel control valve, 10
...Pilot burner air control valve, 11...Catalyst temperature detector, 12.15, 19, 22.29...Comparator, 13...Pilot burner fuel flow rate calculation control unit, 1
4... Fuel flow rate detector, 16.20, 30... Output control calculation section, 17.26... Function generator, 18.28
...Air flow rate detector, 21...Tube temperature detector, 23...Air flow rate calculation section, 24...Adder, 25
...Output current detector, 27...Selector.

Claims (1)

[Claims] In a temperature control device for a fuel cell plant reformer, a tube having a double tube structure filled with a catalyst is heated from the outside with a burner, and the fuel passing through the tube is reformed and supplied to a fuel cell. a temperature detector for detecting the temperature near the burner, a temperature setting device for setting the temperature, and when the detected temperature exceeds the set temperature, the amount of air to be supplied to the burner according to the temperature difference. 1. A temperature control device for a fuel cell plant reformer, comprising a control circuit for adjusting the temperature.